The present invention relates to antimicrobial resin compositions. More specifically, the present invention relates to antimicrobial resin compositions having excellent antimicrobial properties and excellent dispersibility and discoloration resistance.
With recent increasing consciousness of cleanliness of consumers and consumer needs in the pursuance of high-value-added products, it has been promoted to subject products to antimicrobial processing in various fields, for example, stationery such as ball-point pens and erasers, miscellaneous goods of daily use including kitchenware such as cutting boards and bathroom ware such as bathtubs, home electric appliances such as telephone sets, rice cookers, and refrigerators, building materials such as floor materials and wall materials, and textile products such as bed sheets, pajamas, sanitary clothing, and curtains.
There are generally two kinds of methods for subjecting products to antimicrobial processing. In one method, an antimicrobial agent is added to resin and kneaded in the stage of manufacturing products such as plastic molded articles, synthetic textiles and films. The antimicrobial properties of the antimicrobial-processed products obtained by this method last for a long time. In another method, these products are coated with a coating agent containing an antimicrobial agent. The antimicrobial-processed products obtained by this method tend to lose their antimicrobial properties gradually because the coated layer is peeled off through use. Either method is appropriately selected depending on the materials of the commercial products, the manufacturing conditions of the commercial products, the required characteristics, and the types of antimicrobial agents to be used.
On the one hand, antimicrobial agents are classified broadly into organic antimicrobial agents and inorganic antimicrobial agents. Organic antimicrobial agents raise health concerns and many of them do not have sufficient antimicrobial activity. On the other hand, inorganic antimicrobial agents employ metal ions, typically, silver ion, and are excellent in safety and antimicrobial activity. Accordingly, in general, for the above-described products, inorganic antimicrobial agents are used.
The antimicrobial activity of inorganic antimicrobial agents employing metal ions depends on the dissolution rate of the metal ions that are used. When inorganic antimicrobial agents employing metal ions are blended into resin, the metal ions react with additives such as catalyst residue, antioxidant, photostabilizer or the like in the resin and therefore degrade the antimicrobial activity. Moreover, the resin is discolored by light or heat.
In the case of resins molded by methods such as injection molding, extrusion molding or blow molding, antimicrobial agents are generally added to the resin in the stage of masterbatch molding, and it is necessary that antimicrobial agents are dispersed effectively into the resin and on the surface of the resin in order to maximize the antimicrobial ability.
There is a demand for a resin composition that does not change its color to yellowish-brown through light or heat and has excellent dispersibility in a resin and further provides significant antimicrobial properties.